Knife blade renewable cartridge fuse



May 21, 1957 DETCH 2,793,269

KNIFE BLADE RENEWABLE CARTRIDGE FUSE I Filed March 16. 1954 2Sheets-Sheet l FIG.|

INVEN TOR.

ATTORNEY May 21, 1957 DETCH 2,793,269

KNIFE BLADE RENEWABLE CARTRIDGE FUSE Filed March 16.- 1 954' 2Shets-Sheet 2 FIG.|3 13 INVENTOR.

ATTORNEY United States Patent KNIFE BLADE RENEWABLE CARTRIDGE FUSE LewisDetch, Pittsburgh, Pa.

Application March 16, 1954, Serial No. 416,502

11 Claims. (Cl. 200-132) This invention relates to electric circuitbreakers, particularly thermal current breakers, and more especiallyfusible element breakers of the well known thermal type renewablecartridge form.

Those acquainted with the construction, operation and effects of wellknown knife blade cartridge type fuses are well aware that theinsulating bar commonly used to separate the knife blades a precisedistance apart is subject to considerable deterioration, especially atthe most important portions thereof, that is, at the very ends. Thisdeterioration is due to the quite intense heat to which the insulatingbar is often exposed. This intense heat frequently burns or carbonizesthe ends of the insulation bar to such an extent that the materialthereof crumbles away so that the discs abutting the shoulders of theknife blade and supposedly positioned a fixed predetermined distanceapart by the insulating bar, are allowed a certain amount of free motionbetween the shoulders on the knife blade and the ends of the insulatingbar. This free motion of the discs or washers prevents the proper tightclosing of the interior of the fuse by the usual collars on the ends ofthe fuse. The net result is that the venting of the fuse is veryseriously interfered with so that the hot gases and molten metal formedwhen the fuse is subjected to a short circuit current are not properlyconfined and may issue from the fuse in such manner as to easily igniteadjacent inflammable material.

It is also well known to those acquainted with knife blade cartridgefuses of the usual form that the pressure of the usual collars used forholding the knife blades and interior portions of the fuses in placecauses a stress to be placed on the insulating bar tending to cause itto bend or bow and so tilt the usual knife blades in such a manner thatthey are not in one plane through the longitudinal center line of thefuse. As a consequence, it is often very diflicult to insert such fusesin the usual clip provided therefor.

It is also well known that the contact between the usual fuse link andthe usual knife blade is, in most cases, very inefficient with theresult that considerable heat may be generated at this point.

It is also well known to those acquainted with cartridge fuses of theusual form that there is frequently the insufficient heat conductingmetal in contact with the ends of the fuse links.

It is a principal object of my invention to improve the construction ofthe usual knife blade cartridge fuses embodying an insulating spacer barby providing a construction whereby deterioration of the ends of theinsulating spacer bar does not result in misalignment of the spacer bar,fuse links, and knife blade and in which the spacing from the face ofthe usual cartridge closing washers and the usual bolt for retaining thespacer bar and fuse links in place is maintained uniform at all times.

further object of the invention is to provide a device of the typespecified in which the method of confining an end of the fuse link to aknife blade will be such that the tendency to generate heat at thispoint will be decreased and the tendency to distort the ends of the fuselink will be obviated.

A still further object is an improvement in the venting characteristicsof the fuse.

Other objects and advantages will appear as the description of theparticular physical embodiments selected to illustrate the inventionprogresses and the novel features will be particularly pointed out inthe appended claims.

In describing the invention in detail and the particular physicalembodiment selected to illustrate the invention, reference will be hadto the accompanying drawings and the several views thereon, in whichlike characters of reference designate like parts throughout the severalviews, and in which:

Fig. 1 is a side elevational view illustrating the usual knife bladesand connecting spacer bar of a renewable cartridge fuse, without theusual enclosing cylindrical casing, with my invention includued therein.

Fig. 2 is a view of the device of Fig. 1 at a right angle to the view asshown in Fig. 1.

Fig. 3 is a view of the device as shown by Fig. 1 viewed from theopposite side thereof.

Fig. 4 is a transverse sectional view of the device as shown by Fig. 2on the plane indicated by the line lV-IV viewed in the direction of thearrows at the ends of the line.

Fig. 5 is a transverse sectional view of the device as shown by Fig. 2on the plane indicated by the line VV viewed in the direction of thearrows at the ends of the line.

Fig. 6 is a view of a fragment of one end of a fuse link assemblysimilar to that shown in Fig. 1 illustrating another form of myinvention.

Fig. 7 is a longitudinal sectional view of the device of Fig. 6 on theplane indicated by the line VII-.VII viewed in the direction of thearrows at the ends of the line.

Fig. 8 is a transverse sectional view of the device as shown by Fig. 7on the plane indicated by the line VIII-VIII viewed in the direction ofthe arrows at the ends of the line.

Fig. 9 is a fragmentary view of one end of a fuse link assembly such asis shown by Fig. 1 illustrating a modified form of my invention.

Fig. 10 is a side elevational view of the device as shown by Fig. 9.

Fig. 11 is a transverse sectional view of the device as shown by Fig. 10on the plane indicated by the line XI.XI viewed in the direction of thearrows at the ends of the line.

Fig. 12 is a view similar to Figfll but illustrating a "ice modifiedconstruction of the device as shown by Fig. 11

Fig. 13 is a fragmentary view of one end of a fuse link assembly such asis shown by Fig. 1 illustrating a modified form of my invention.

Fig. 14 is a transverse sectional view of the device as shown by Fig. 13on the plane indicated by the line XIV-XIV viewed in the direction ofthe arrows at the ends of the line.

Fig. 15 is a fragmentary view of one end of a fuse link assembly such asis shown by Fig. 1 illustrating a further modified form of my invention.7 I

Fig. 16 is a side elevational view of the device as shown by Fig. 15.

Fig- 17 is a transverse sectional view of the device as shown by Fig. 16on the plane indicated by the line XVIIXVII viewed in the direction ofthe arrows at the ends of the line.

ln Fig. l, I have shown a fuse link assembly embody in Figs. 2, 3, 4 and5 there is illustrated the usual pair of knife blades 1 and 3. Eachknife blade has a wider outer end, as 5 and a narrow inner end as 7,best shown in Fig. 3. At the juncture between the wider outer end andthe narrow and inner end of each knife blade is a closing end washer, as9 and 11, formed with slots 10, 12, respectively, through which slotsthe knife blades extend. The knife blades are connected and held aproper distance apart by the insulating spacer bar13. This spacer bar isattached to the knife blade by bolts as and 17. The fuse linksconnecting the knife blade is designated 19.

The parts hereinbefore just above described are quite usual in renewableknife blade fuses and it is not uncommon to find the spacer bar 13attached to each knife blade by a pin, as 21, passing through the spacerbar and the narrow inner end of a knife blade.

Usuallya plain nut or plain nut and washer are on the free end of thebolts, as 15, that is, on the lower end thereof, as viewed in Fig. 2. Inmy construction, however, I have a retaining fastener, as 23 and 25,having a screw-threaded through orifice therein into which the end of abolt, as 15, may be threaded. This retaining fastener 23 has ample areato bear against the fuse link 19 so that good heat conductivity existsbetween the retaining fastener 23 and the fuse link 19. In addition theretaining fastener 23 frictionally presses the fuse link 19 into closecontact with the face of the narrow inner end of the. knife blade, sothat good electrical and thermal conductivity are both obtained. Inaddition, the retaining fastener, as 23, has, as best shown in Fig. 5,two fingers 27 and 29. These receive between them a tongue 31 whichprevents the retaining fastener 23 when being screwed into place by theturning of a bolt, as 15, from turning with the bolt and deforming orpushing the fuse link out of place. In short, the construction of theretaining fastener 23 is such that in drawing it into place there is no.injuryto the fuse link 19 and a much more efficient thermal andelectrical contact is secured between the end of the fuse link and theadjacent metallic electrical and heat conducting parts.

The tongue, as 31, and the similar tongue, as 33, are each a part of aspacer bar receiving saddle, as 35 and 37. This spacer bar receivingsaddle is formed with a bottom plate 39 and side pieces, as 41 and 43,so that the ends of a spacer bar are nicely housed in the saddle. Eachsaddle, in addition, is formed with two depending fingers,

one on each side. One of the depending fingers on saddle 37 at the lefthand end of Fig. 2, is designated 45. The two depending fingers onsaddle 35, shown at the right hand end of Fig. 3, are designated 47 and49. The

depending fingers may also be seen in Fig. 5 which shows bore receives abolt, as 17, so that the bolts, as 15 and t 17, pass through the spacerbar, a saddle, such as 37 or 35, the inner end of a knife blade, as 7 or55, the fuse link 19 and a retaining fastener as 23 or 25 therebybinding all together tightly.

It will be observed that tongue 33 passes through a slot, as 57, in aninner end of a knife blade, such as 7, as shown at the right hand end ofFig. 2. This slot has one side in the plane of the inner face of an endwasher, as 9, and the opposite side of the slot is positioned so thatthe tongue, as 33, is frictionally and closely positioned therein sothat the distance between a bolt, as 15, and the inner face of an endwasher, as 9, is always maintained completely uniform.

In the device as shown by Figs. 1 to 5 inclusive, a

tongue, as 33, is shown as a part of a saddle, as 35. I I

may also make the tongue a portion of the retaining fastener. Suchconstruction is shown in Figs. 6 to 8 inclusive. In these views, thetongue is designated 59 and passes through a slot 61 in the inner narrowportion 63 of a knife blade. The tongue 59 is a projection on one end ofa retaining fastener 65 which rests against one face of a fuse link 19and is retained in place by being formed with a through screw-threadedbore 67 adapted for the reception of a screw-threaded bolt, as 69. Thescrewthreaded bolt, as in the other forms, retains the spacer bar 13,the saddle 71, the knife blade 63, the fuse links 19 and the retainer 65tightly in place together.

In Figs. 9, l0 and 11 I illustrate a construction in which I employ aretaining fastener 73 like the retaining fastener 65 of Fig. 7, but Ialso employ a nut 75 on the end of the bolt 77 holding the spacer bar 13and the link 19 and the other parts firmly together.

As shown by Fig. 11, the bolt 77 may be screw-threaded into the innernarrow end of the knife blade 79 and screw-threaded into the nut 75.However, I may employ an alternative construction as shown in Fig. 12 inwhich the bolt 81 is screw-threaded into the retaining fastener 83 andinto the nut 75, but not into the inner narrow end of a knife blade 85.

Figs. 13 and 14 show another construction in which the spacer bar 13,fuse link 19, knife blade 87 and retain ing fastener 39 are heldtogether by a bolt 91 which is screw-threaded into a throughscrew-threaded bore 93 and has a flange 95 permanently attached to itsupper end as viewed in Figs. 13 and 14.

Figs. 15, 16 and 17 illustrate a construction in which the end washer 97is provided with projections or nubs, best shown in Fig. 17, andnumbered 99, 101, 103 and 105. These nubs closely contact and restrainthe tongue 107 of the retaining fastener 109 and also contact closelyand restrain spacer bar 13 and the knife blade 111.

An advantage common to all the described forms of the invention is thatthe respective tongues, insofar as they extend across the slots of theend washers or discs on the inside thereof and in contact therewith,block or seal said slots against the exit of gases and molten metal soas to retard and baflde said exit.

Although I have particularly described a preferred physical embodimentof my invention and modified forms thereof, nevertheless, I desire tohave it understood that the forms selected are merely illustrative, butdo not exhaust the possible physical embodiments of the idea of meansunderlying my invention.

What I claim as new and desire to secure by Letters Patent is:

1. In a renewable fuse having a pair of knife blades, each knife bladehaving a narrow inner end and a wider outer end, said blades beingdetachably connected together by both an insulating spacer bar and afuse link, said bar and link being contained within an insulatinghousing, end washers for sealing the space be tween the knife blades andsaid housing, said washers having a central slot to receive the narrowinner portion of the blades so that the washers are disposed between thewide outer portion of the blades and the ends of the spacer bar, andbolts, one passing through each narrow inner end of each blade and theinsulating spacer bar, the invention which comprises a through slotformed in the narrow inner end of one of said blades, which slot has oneedge in the plane of the inner face of the adjacent end washer, and ametal tongue pass ing through said slot, said tongue bearing on one sideagainst the inner face of the adjacent end washer and on the otheropposite side against a side of said slot whereby the end washer andblade are held firmly togather, and a metal body through which one ofthe.

said bolts extends and of which the tongue forms a part.

2. The device as specified in claim 1 in which the metal body forms asaddle receiving an end of the spacer, bar.

3. The device as specified in claim 1 in which the metal body forms aretaining fastener for an end of the link.

The device as specified in claim 2, in which there is a fiatlinkretaining washer screw-threaded onto oneof the said bolts and formedwith two fingers, one on each side of a tongue whereby the washer isprevented from turning when the bolt is turned.

5. The device as specified in claim 2 in which the saddle is formed withdepending fingers, one on each side each resting against an edge of theinner narrow end of a blade.

6. The device as specified in claim 3 in which there is a saddlereceiving an end of the spacer bar and through which one of the saidbolts passes.

7. The device as specified in claim 3 in which each bolt is providedwith a nut screwed thereon and the metal body is provided withscrew-threaded bolt receiving through bore.

8. The device as specified in claim 3 in which the metal body is formedwith a through screw-threaded orifice and the bolt is screw-threadedtherethrough with the head thereof against the metal body and a fixedflange on the free end of the bolt.

9. The device as specified in claim 3 in which the end washers areprovided with inwardly extending inner nubs between which the tonguelies and between which the inner end of a blade and the adjacent end ofa spacer bar are positioned in close contact.

10. In a renewable fuse having a pair of knife blades, each knife bladehaving a narrow inner end and a wider outer end, said blades beingdetachably connected together by both an insulating spacer bar and afuse link, said bar and link being contained within an insulatinghousing, end washers for sealing the space between the knife blades andsaid housing, said washers having, a central slot to receive the narrowinner portion of the blades so that the washers are disposed between thewide outer portion of the blades and the ends of the spacer bar, andbolts, one passing through each narrow inner end of each blade and theinsulating spacer bar, the invention which comprises a through slotformed in the narrow inner end of one of said blades, which slot has oneedge in the plane of the inner face of the ad jacent end Washer, and aconductive metal body having a portion formed with a through bore, oneof said bolts passing through said bore, said body further having atongue passing through said last mentioned slot, said tongue bearingagainst the inner surface of the adjacent end washer and the oppositeside of said tongue bearing against a side of said last mentioned slot,and means engaging said bolt and firmly connecting together in fixedspaced relation said blade, said washer, said bolt, said body and saidspacer bar, said tongue further extending across said slot of said endwasher to baffle the exit of gases from said slot.

11. In a device according to claim 10, said last mentioned means beingscrew threads formed in said first mentioned portion of said conductivemetal body.

References Cited in the file of this patent UNITED STATES PATENTS1,092,153 Mallory Apr. 7, 1914 1,702,355 McDonald et al Feb. 19, 19291,907,739 Clark May 9, 1933 2,198,663 Floten Apr. 30, 1940 2,521,600Pflaum Sept. 5, 1950 2,556,018 Von Hoorn June 5, 1951

